Mail cannot log into accounts after El Capitan

after upgrading to 10.11 I lost the ability to log into my earthlink POP accounts ....

Try to delete MailData folder from username//Library/Mail/V3.

Mail Application will import again the mailboxes from all your accounts.

I hope this helps.

I Tried this, I still cannot access my exchange email account. Same issue: cannot verify.

What you did on your MB Pro should not affect your iPhone in any way, Even if you have the two set to sync they would not be syncing account information.

Focusing on the Mac for the time being, when you go to the menu bar and choose Window > Connection Doctor, do you get all green dot indicators for your accounts? If not, what is the error message that is presented to the right of the dot indicator? This may help in narrowing down the issue.

OK, and you stated that you confirmed that your password is correct by logging into your email online with the same email and password, correct?

That error message that you're receiving is directly related to the login credentials for that specific email account (Email/Password) -- more specifically it's referring to SMTP, which is the outgoing server (IMAP or POP would be the incoming server).

Go ahead and go into your Mail application > Click Mail in the top left menu bar > Choose Preferences > Choose Accounts > Choose the email account you're experiencing issues with (if you have more than one listed).

Once you're within the email account preferences make sure you're under the "Account Information" tab. Delete the password that appears about halfway down and re-enter it, making certain it's the same password you used successfully to login to your email web portal. Then in the "Outgoing Mail Server (SMTP)" section, choose "Edit SMTP server list". Choose the server name in the list that you use as your outgoing email server. Under the "Advanced" tab, be certain that your email and password are listed. Once again, delete what's in the password field and re-enter the password you know to be correct. Than click "OK", click the red circle to close out of the "Accounts" window. Choose to Save/Apply changes when prompted.

Then go back to Window (in the menu bar) > Connection Doctor and have a look and see if you get all green indicator dots now.

Good luck!

OK, so your issue is definitely related to your email password then.

Sorry if you already mentioned this, but is the email account you are using POP or IMAP? If it's IMAP, I'd recommend backing up (exporting) the mailboxes that currently have email on your Mac just out of precaution, and then delete and re-add the email account(s) from within the Mail Preferences > Accounts section and have it pull in the necessary server info again. If the error appears again at that point in time during setup then there's not much other explanation other than the fact that your login information has to be incorrect.

Import or Export Mailboxes

I seem to have a similar, but not quite as extensive problem. On my MacBook Pro, and my wife's Mac Mini, all of our POP accounts appear to work fine... but my APPLE iCloud email has somehow lost the name of the "Outgoing Mail Server". It only has my POP Outgoing servers listed. Can someone PROVIDE the name of the iCloud (IMAP) Outgoing Server? THANKS!

(ps: the Connection Doctor indicates solid green for ALL accounts)

David L. Gerhardt: Linked below is the article that provides the server information for iCloud email accounts.

IMAP (Incoming) Server Info:

• Server name: imap.mail.me.com
• SSL Required: Yes
  If you see an error message when using SSL, try using TLS instead.
• Port: 993
• Username: This is usually the name part of your iCloud email address (for example, emilyparker, not emilyparker@icloud.com). If your email client can't connect to iCloud using just the name part of your iCloud email address, try using the full address.
• Password: Your iCloud password

SMTP (Outgoing) Server Info:

• Server name: smtp.mail.me.com
• SSL Required: Yes
  If you see an error message when using SSL, try using TLS or STARTTLS instead.
• Port: 587
• SMTP Authentication Required: Yes
• Username: Your full iCloud email address (for example, emilyparker@icloud.com, not emilyparker)
• Password: Your iCloud password

https://support.apple.com/en-us/HT202304

Hope this helps!

As long as you export the mailboxes, delete the account, and then re-add the account you should be fine. POP will pull in some email (and depending on your settings, maybe all of your email) when you re-add the account. Exporting the mailboxes is just a precaution in case you delete the account and upon re-adding the emails don't come back you can then import those exported mailboxes back into the Mail app.

So, yes, you should be OK to delete and re-add the account as long as you export mailboxes with email in them first.